After a 30 min equilibration period ,vessels were contracted with 2 x 10-7 mol/L NE,and then adding Ach,L - NNA,L - Arg and so on ,to record the changes of tension of vessels ring.

• 经30分钟平衡后，每个血管环用去甲肾上腺素（NE，2 x 10刁 moVL）预收缩，达最大收缩状态再分别加人乙酚胆碱水－硝基－L－精氨酸上一精氨酸等药物记录动脉环的张力变化。